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Wednesday, February 1, 2012

Cruciferous Mini Chemistry Lesson

I was at the doctor yesterday and got a question by text
about whether green smoothies were unhealthy and I was completely perplexed why
anyone would think that.Sure you can
make an unhealthy green smoothie by loading it up with fruit and eliminating
the kale and adding a little spinach instead. However the person who asked this
question is a fan of healthy green smoothies with kale so I knew something was
up.We texted back and forth for a while
and I called her and we talked about it and got everything cleared up. Once I
got home the email questions started flooding in and that was when I knew I had
really needed to write this post for everyone who was confused but didn’t have
anyone to ask about this. So much for my day off, darn it!*ugh*

I make my green smoothies with kale for a number of reasons
but the primary one is that kale is the most nutritious raw and I think works
well in smoothies from a flavor perspective.However kale (like all cruciferous veggies) is generally more nutritious
when eaten raw which I will explain so that you understand the process and
aren’t confused the next time someone writes something to the contrary. When I
first heard about this controversy the first thing I thought of was the comment
I wrote yesterday about being careful what you read in popular books, clearly
the same thing goes for what you read on blogs.

All vegetables contain protective micronutrients and
cruciferous veggies are no exception.If
you were to look at the cells of kale under a microscope you would see each one
contained a number of separate items included myrosinase (enzyme) and glucosinolates
(organic compound) inside a vacuole (membrane). Think of myrosinase and
glucosinolates like chickpeas and tahini before they are combined into hummus.
When kale leaves are intact (whole) the myrosinase is physically separated from
the glucosinolates. (1)However in order
for the cruciferous veggies to form indoles and isothiocyanates the myrosinase
and glucosinolates need to be combined. (1) They can be combined by blending,
chopping or chewing. (2)Obviously
blending does a more complete job of breaking down the cell walls releasing the
maximum amount of myrosinase so it can combine with the glucosinolates.However it is also important to know that myrosinase
is inactivated by heat (cooking) (3).If
you cook whole or roughly chopped kale you are getting significantly less of
the indoles and isothiocyanates (ITCs) because of the reduction in myrosinase.The human digestive tract does have some
myrosinase activity but the absorption of the ITCs is substantially lower for
cooked cruciferous veggies according to numerous studies. (4)Glucosinolates are water-soluble so boiling
is not a good way to prepare cruciferous veggies. (5)Boiling (2), steaming (3) and microwaving (6)
are thought to completely inactivate myrosinase making the cruciferous
vegetables far less nutritious.

Why should we care about our absorption of ITCs?ITCs are critical for optimal human health
since they not only kill cancer cells (7) but they remove carcinogens in both
the phase I and II processes. (4) Additionally ITCs are anti-inflammatory (8),
induce cancer cell-cycle arrest (7) and have been shown to eradicate H. pylori
(9) (a major cause of stomach cancer). A better question might be why wouldn’t
you want to absorb as many ITCs as you possibly could?

Why do we need indoles?In the acidic environment of the human stomach indole-3-carbinols (I3Cs)
combine to form acid condensation products (10) which include:dimer 3,3’-diindolmethane (DIM) and cyclic
trimer (CT).The biological activity of
DIM and CT differ from I3C but I3C is typically credited for the effects.Both these (DIM and CT) form to a lesser
degree when myrosinase has been inactivated by cooking. (11)I3Cs have been found to inhibit estrogen
activity and thereby are thought to decrease estrogen-sensitive cancers (think
breast and prostate). (12)Additionally
I3Cs also have anti-angiogenic (13) properties (stop the growth of blood
vessels to cancerous tumors) and they induce cell death (14) (apoptosis).I3Cs have been shown to eradicate
precancerous cervical lesions in some women. (15)I don’t know about you, but I say bring on
the I3Cs and as many as possible which means more raw cruciferous vegetables
please.

First, I apologize for all the endnotes but when something
is put out without any backup I worry that no one will have any confidence in
the information that is being provided. I will not be boring you with endnotes
often going forward but I thought it was necessary in this post.

Here is the bottom line for me.Consuming cruciferous vegetables is important
for our health.Based on the science I
have read blending raw kale is not only healthy but is the healthiest way to
consume your kale.As with everything
else I will continue to stay current on the latest science on this topic and if
anything changes I will let you know. Until I see scientific research that
tells me that raw pureed kale is unhealthy I will continue to enjoy green
smoothies (made with copious amounts raw kale I might add) most days of the
week.Dan and I both had green smoothies
for breakfast this morning if you are curious.;-)

Making a healthy green smoothie is easy and you all know
what I am going to say based on what you see me prepare. First include a lot of
raw kale in your smoothies.Frozen
banana added to the mix makes the smoothie creamy.Including walnuts and flaxseeds for healthy
fats assists your body to absorb the fat-soluble vitamins in the kale.Cinnamon is also added to our green smoothies
for additional antioxidants as well as flavor.Vanilla is included because it smoothes out the sharpness of the greens
allowing me to add much more of them to our smoothies.You can also add frozen cherries and cocoa
powder for flavor and antioxidants. That is how you make a delicious and
healthy green smoothie.

Calories Burned Chewing:

This is just a side issue but I am mystified that anyone
would believe chewing kale could result in 100 calories being burned.*scratches head* It takes 1 mile, either
running or walking to burn 100 calories and that is using the largest muscles
in the human body.Let’s think about that
for a minute. If you walk a mile in 15 minutes you are using your legs and
buttocks to generate movement and that burns 100 calories. The muscle mass of
those muscles is what at least 100 times greater than your jaw muscles, and
probably more? So that would imply that you would need to chew for at minimum
of 1500 minutes (15 times 100) to burn 100 calories.Since there are only 1440 minutes in a day I
find it impossible to see how this math works.

Signing off:

I appreciate that so many of you wrote to ask me what I
thought about green smoothies.Your
faith in my ability to cut through the controversy and give you the truth has
really touched me.I would prefer to give up my day off if it
means that I can clarify things for you.I wanted to include plenty of endnotes so that you could follow the
science for yourself if you choose, or at least realize that this wasn’t just “my
opinion on the matter” but rather there is hard science which backs up
everything that I wrote.Now I am going
to try to enjoy the rest of my “day off”.

If you ever see anything that confuses you in the future
just ask me. If I don’t know the answer I will do my research and find out for
all of us.

22 comments:

Thank you SO MUCH for your insights on this. The "Green Smoothies are not good" take comes from Dr. T. Colin Campbell and others and so it had me very confused. Perhaps they should define a "green smoothie", maybe they are talking about something other than what I make (which is similar to yours).

You are very welcome. I got so many email questions about this I knew I had to write it. I don't read Happy Herbivore (nor did I read her post on this) but I have to say I am completely shocked that Dr. Campbell would say that. I feel like it must have been taken out of context or based on how "green smoothies" were defined like you said. Everything that I have seen tells me that raw blended kale is the most nutritious way to eat kale. I know that some people don't find green smoothies to be filling and that could cause them to eat something in addition to the smoothie which could cause weight gain. But otherwise I can't even guess why a green smoothie made with a lot of kale and a little fruit would be unhealthy.

Sometimes you read things and they just don't add up. Burning 100 calories chewing is one of those times.

They make supplements for almost everything. IMO it is always better to get our nutrition from food. There is a lot that science doesn't know about how different phytochemicals interact. For all we know DIM may require a number of other phytochemicals in order to be absorbed and therefore the supplement isn't doing anything. Also supplements are most often a man-made version of the naturally occuring item and those tend to not be well absorbed. I guess you can tell I am not a big fan of supplements in general. Thanks for the question, I am sure you aren't the only one who was wondering about that.

I know I've never commented before but I've been reading your blog for over a year at least now! Anyway, I watched as this whole controversy blew up yesterday over Twitter and Facebook, and just wanted to say THANK YOU for being a voice of reason here. It's so comforting to know that I'm not crazy! I'm very grateful for your thorough, level-headed, and fact-based approach.

I heard about the controversy blowing up on Twitter and Facebook and was in shock. Not being a fan of drama I wasn't certain what to make of it initially. When I starting getting emails asking me if they should throw out their blender I knew things were out of control. I study nutrition every day and I haven't seen any science that would indicate raw blending kale is in any way unhealthy.

thanks so much for commenting and letting me know that you agree, it is comforting not to be alone on this,Ali

THANK YOU!!! This was such a relief to read. I'm 11 weeks pregnant, and even though I loved eating steamed vegetables before I got pregnant, now I can't stand them! The only way I've been able to get my greens in is by eating them in green smoothies (and I don't include a lot of fruit in my smoothies). I was a little confused because it usually takes me an hour or more to finish a green smoothie, and then I'm full for several hours afterward--definitely not something I just suck down in a few minutes and then feel hungry an hour later.

But I'm sorry that you had to do this on your day off. :( Still, I'm incredibly appreciative of your thorough and scientifically-back response to the whole thing. Thanks again!

You are very welcome. Raw blended kale is more nutritious than cooked from everything I have read on the subject. It takes me a while to drink a smoothie too and they keep me full for 4 or 5 hours. Also my hubby has forgotten to fast and had smoothies before blood tests and his blood glucose was 103 approximately 45 minutes after the smoothie which told me they weren't elevating his glucose since his fasting level is usually upper 70s or low 80s.

Please don't be sorry, I would much rather have done this since I knew people were confused. I got over 20 emails asking me about it and could only imagine how many people wanted to know but didn't know who to ask. If you ever have another question please feel free to ask. I am happy to help anytime. Research is something that I enjoy, so if I don't know the answer I like the search for it.

I'd like to add to the "thank you!" club! I won't pick on her, but I KNOW I can trust your endless research and knowledge. I've changed a lot of things since starting to read your blog, and will continue to do so ;-)

You are very welcome! If you ever see anything and aren't sure what to believe please ask. I am happy to help any way that I can. Awwww, thank you so much! It is very nice to hear that I have helped. :-)

Another "thank you" from me, too! I thought her whole post (and many of her others, actually) was total bollocks, so it's good to have it confirmed here. I prefer spinach in my smoothies to kale, partly for texture, but partly because I really don't like spinach by itself but love kale. Blending it is one of the only ways I can convince myself to eat spinach. :)

If you are going to cook your kale just be sure to cut it up finely (I usually shred it) so that the myrosinase can combine with the glucosinolates before the heat destroys the myrosinase and you should be fine.

Have you ever tried shredding the spinach and then adding it to soup or salads? Also you could make salads with some spinach but also include other greens that you do like. I enjoy putting raw spinach in the bottom of my soup bowl and covering it with hot soup to wilt it. My favorite use of spinach is probably in savory oatmeal? Have you given that a try? Then there is the way they make spinach at Jaleo which is lightly wilted with garlic, golden raisins and green apple. I bet one of those might work for you. ;-)

Salads are the only other way I like spinach, and it has to be the raw baby stuff. I don't like the slimy texture it gets when wilted or heated in any way (except if finely chopped in curries or ravioli). I like most other greens raw or wilted, though. Maybe the answer is to stop buying spinach and switch entirely to kale, chard, etc.

It does sound like maybe you need to stop buying spinach except for salad. I am not crazy about if it is cooked more than about 30 seconds myself so I understand. Sounds like the texture bothers you more than me though.

I love the citations - it's so refreshing and important on issues such as this.

From everything that I have read, many of the fruits we do add to a green smoothies are nutritious power houses - blueberries, strawberries, cherries - I don't think anyone could overdo them at the rate of a cup of berries in a huge blender of greens and banana! I could never eat as much kale or fruit at a time if I just ate it raw. Blending allows one to maximize the nutrition.

After all the controversy I felt like I had to write this. I thought the references waere necessary this time, but don't expect to see those often since it takes a lot longer to write using them.

I agree with you on the issue. When I make green smoothies I get more kale and more berries and both are good for you. I am guessing that the issue was too much fruit, not enough kale and that resulted in too many calories. Since most people are overweight in North America excess calories becomes a big issue. But that is only a guess since the original post didn't provide any "real information" to back up why green smoothies weren't healthy. I don't respond very well to "change because I told you to" without knowing why.

THank you, you inspired me to make a smoothie (er. instead of dinner, haha). 2 kale leaves, 2 collard leaves, some almond milk, blueberries and a banana and two drops of stevia. It was delicious! I like your side bar traffic viewer...a lot of people view your blog! Wow!

We have smoothies for dinner sometimes too, they are great when you don't feel like cooking. ;-) Great minds think a like. I love the sound of your smoothie BTW.

The traffic viewer on my blog is the free version. Follow the link from my blog to install it on yours. Dan is always shocked by the traffic the blog gets, and I have to say I am a bit surprised too. It is interesting to see all the different locations of readers.

Ali, thanks for the well-researched article. I am hypothyroid and have always read that I should avoid raw kale and spinach because of their "goitergenic" qualities. What are your thoughts on this? Thanks!

Sorry for the delay in my response, life has been busy and I wanted to research my answer before I replied. Raw kale is part of the cruciferous family and as such does contain goitrogens which are inactivated by cooking. However I haven't seen anything that indicates raw spinach is an issue. Also I would suggest that you check with your doctor since everything that I read referred to "untreated" thyroid problems which I assumed isn't you. Other foods which are goitrogens and not in the cruciferous family which you should know about include: millet, peanuts, pine nuts, and soy beans. Additionally have you had your iodine level checked? If you live in the midwest this population has more trouble with iodine deficiency. Since iodine is required for the thyroid to create hormones that would be something I would look into if I were you.